628 research outputs found
More Evidence for Variable Helium Absorption from HD 189733b
We present a new Keck/NIRSPEC observation of metastable helium absorption
from the upper atmosphere of HD 189733b, a hot Jupiter orbiting a nearby
moderately active star. We measure an average helium transit depth of % integrated over the [-20, 20] km/s velocity range. Comparing this
measurement to eight previously published transit observations with different
instruments, we find that our depth is 32% (9) lower than the average
of the three CARMENES transits, but only 16% (4.4) lower than the
average of the five GIANO transits. We perform 1D hydrodynamical simulations of
the outflow, and find that XUV variability on the order of 33%--common for this
star--can change the helium absorption depth by 60%. We conclude that changes
in stellar XUV flux can explain the observational variability in helium
absorption. 3D models are necessary to explore other sources of variability,
such as shear instability and changing stellar wind conditions.Comment: Published by A
Frailty and Risk of Falls, Fracture, and Mortality in Older Women: The Study of Osteoporotic Fractures
Background. A standard phenotype of frailty was associated with an increased risk of adverse outcomes including mortality in a recent study of older adults. However, the predictive validity of this phenotype for fracture outcomes and across risk subgroups is uncertain. Methods. To determine whether a standard frailty phenotype was independently associated with risk of adverse health outcomes in older women and to evaluate the consistency of associations across risk subgroups defined by age and body mass index (BMI), we ascertained frailty status in a cohort of 6724 women ≥ 69 years and followed them prospectively for incident falls, fractures, and mortality. Frailty was defined by the presence of three or more of the following criteria: unintentional weight loss, weakness, self-reported poor energy, slow walking speed, and low physical activity. Incident recurrent falls were defined as at least two falls during the subsequent year. Incident fractures (confirmed with x-ray reports), including hip fractures, and deaths were ascertained during an average of 9 years of follow-up. Results. After controlling for multiple confounders such as age, health status, medical conditions, functional status, depressive symptoms, cognitive function, and bone mineral density, frail women were subsequently at increased risk of recurrent falls (multivariate odds ratio = 1.38, 95% confidence interval [CI], 1.02-1.88), hip fracture (multivariate hazards ratio [MHR] = 1.40, 95% CI, 1.03-1.90), any nonspine fracture (MHR = 1.25, 95% CI, 1.05-1.49), and death (MHR = 1.82, 95% CI, 1.56-2.13). The associations between frailty and these outcomes persisted among women ≥ 80 years. In addition, associations between frailty and an increased risk of falls, fracture, and mortality were consistently observed across categories of BMI, including BMI ≥ 30 kg/m2. Conclusion. Frailty is an independent predictor of adverse health outcomes in older women, including very elderly women and older obese wome
A data-driven approach to constraining the atmospheric temperature structure of KELT-9b
Context. Observationally constraining the atmospheric temperature-pressure
(TP) profile of exoplanets is an important step forward for improving planetary
atmosphere models, further enabling one to place the detection of spectral
features and the measurement of atomic and molecular abundances through
transmission and emission spectroscopy on solid ground. Aims. The aim is to
constrain the TP profile of the ultra-hot Jupiter KELT-9b by fitting synthetic
spectra to the observed H and H lines and identify why
self-consistent planetary TP models are unable to fit the observations.
Methods. We construct 126 one-dimensional TP profiles varying the lower and
upper atmospheric temperatures, as well as the location and gradient of the
temperature rise. For each TP profile, we compute transmission spectra of the
H and H lines employing the Cloudy radiative transfer code,
which self-consistently accounts for non-local thermodynamic equilibrium (NLTE)
effects. Results. The TP profiles leading to best fit the observations are
characterised by an upper atmospheric temperature of 10000-11000 K and by an
inverted temperature profile at pressures higher than 10 bar. We find
that the assumption of local thermodynamic equilibrium (LTE) leads to
overestimate the level population of excited hydrogen by several orders of
magnitude, and hence to significantly overestimate the strength of the Balmer
lines. The chemical composition of the best fitting models indicate that the
high upper atmospheric temperature is most likely driven by metal
photoionisation and that FeII and FeIII have comparable abundances at pressures
lower than 10 bar, possibly making the latter detectable. Conclusions.
Modelling the atmospheres of ultra-hot Jupiters requires one to account for
metal photoionisation. [abridged]Comment: Accepted for publication by A&
UK Housing Market: Time Series Processes with Independent and Identically Distributed Residuals
The paper examines whether a univariate data generating process can be identified which explains the data by having residuals that are independent and identically distributed, as verified by the BDS test. The stationary first differenced natural log quarterly house price index is regressed, initially with a constant variance and then with a conditional variance. The only regression function that produces independent and identically distributed standardised residuals is a mean process based on a pure random walk format with Exponential GARCH in mean for the conditional variance. There is an indication of an asymmetric volatility feedback effect but higher frequency data is required to confirm this. There could be scope for forecasting the index but this is tempered by the reduction in the power of the BDS test if there is a non-linear conditional variance process
Classic yin and yang tonic formula for osteopenia: study protocol for a randomized controlled trial
<p>Abstract</p> <p>Background</p> <p>Osteoporosis is a growing worldwide problem, with the greatest burden resulting from fractures. Nevertheless, the majority of fractures in adults occur in those with "osteopenia" (bone mineral density (BMD) only moderately lower than young normal individuals). Since long-term drug therapy is an expensive option with uncertain consequences and side effects, natural herbal therapy offers an attractive alternative. The purpose of this study is to evaluate the effect on BMD and safety of the Classic Yin and Yang Tonic Formula for treatment of osteopenia and to investigate the mechanism by which this efficacy is achieved.</p> <p>Methods/design</p> <p>We propose a multicenter double-blind randomized placebo-controlled trial to evaluate the efficacy and safety of the Classic Yin and Yang Tonic Formula for the treatment of osteopenia. Participants aged 55 to 75 with low bone mineral density (T-score between -1 and -2.5) and kidney deficiency in TCM will be included and randomly allocated into two groups: treatment group and control group. Participants in the treatment group will be treated with Classic Yin and Yang Tonic Granule, while the controlled group will receive placebo. Primary outcome measure will be BMD of the lumbar spine and proximal femur using dual-energy X-ray absorptiometry. Secondary outcomes will include pain intensity measured with visual analogue scales, quality of life, serum markers of bone metabolism, indices of Neuro-endocrino-immune network and safety.</p> <p>Discussion</p> <p>If the Classic Yin and Yang Tonic Formula can increase bone mass without adverse effects, it may be a novel strategy for the treatment of osteoporosis. Furthermore, the mechanism of the Chinese medical formula for osteoporosis will be partially elucidated.</p> <p>Trial registration</p> <p>This study is registered at ClinicalTrials.gov, <a href="http://www.clinicaltrials.gov/ct2/show/NCT01271647">NCT01271647</a>.</p
Background risk of breast cancer and the association between physical activity and mammographic density
This work is licensed under a Creative Commons Attribution 4.0
International License. The images or other third party material in this
article are included in the article’s Creative Commons license, unless indicated
otherwise in the credit line; if the material is not included under the Creative Commons
license, users will need to obtain permission from the license holder to reproduce the
material. To view a copy of this license, visit http://creativecommons.org/licenses/
by/4.0
- …